Screen seal for hammer mills



g- '193& R. D. MECDONALD 2,125,352

SCREEN-SEAL FOR HAMMER MILLS Filed July 5, 1935 Patented Aug. 2, 1938 UNITED STATES PATENT OFFICE SCREEN SEAL FOR HAMMER- MILLS Application July 5, 1935, Serial No. 29,780

4 Claims.

The invention relates to an improvement in hammer mills.

In hammer mills of the upright or vertical type,- there is provided a cylindrical drum or housing, the inner periphery of which is lined with a screen. The drum includes a hinged cover portion, which may be swung upwardly to expose the interior of the mill. A section of the screen lining is carried by the cover. Consequently at the hinge between the cover and drum casing there is necessarily a break in the screen lining, leaving a gap in the screen, through which material in process within the drum objectionably leaks. To prevent such leakage it is desirable to provide a seal to bridge this gap in the screen when the cover is closed.

The main object of the invention, therefore, is to provide a screen seal for the purpose mentioned.

Another object of the invention is to provide such a seal of simple inexpensive construction that can be operatively associated with standard hammer mills without altering the structure of the mill.

Still another important object is to provide such a seal which automatically assumes its screen gap bridging position when the cover for the drum is closed.

Other important objects will become apparent as the disclosure is more fully made.

The improvement may be applied in one practicable embodiment to a hammer mill of the socalled vertical type having an upright substantially cylindrical drum, the inner periphery of which is lined with a screen, a portion of which is carried by a cover and removable therewith.

The gap between adjacent ends of the screen sections. on the cover and in the drum is closed by a seal in the form of the plate. Securely fastened to the cover adjacent its hinge, so that, when the cover is in its closed position, the seal plate bridges the gap and closely overlaps adjacent ends of the screen sections. Within the drum is mounted the usual rotor carrying peripheral hammers that cooperate with the screen to reduce the material in process. Of course, the drum includes means to feed material thereinto and means to remove reduced material therefrom.

This improved structure is shown in detail in the accompanying sheet of drawing, wherein:

Figure 1 is a vertical longitudinal sectional view through a standard type of vertical hammer mill showing the novel seal structure operatively associated therewith; and,

Figure 2 is a detail perspective view of a fragment of the drum and cover to illustrate the seal on a somewhat enlarged scale.

The mill shown embodies a base l0, carrying an upright casing in the form of a substantially cylindrical drum I I lined with a peripheral screen l2. Near its top the drum carries a bracket I3 for mounting a hinge pin 14, to which in turn is connected a bracket hinge [5 for carrying a hinged cover Hi. This cover carries a section I! of the screen. Thus a break or gap occurs between adjacent ends of the screen sections I2, I! adjacent the hinge [4.-

The drum carries a shaft I 8 for driving and mounting a rotor disk I9, the periphery of which carries hammers cooperating with the screen in reducing material fed into the drum in any conventional manner not illustrated. The drum at its bottom is provided with a pocket 2! to receive stones or other chunks of foreign material accidentally fed into the drum. One portion of the screen l2 at [2 is open so that reduced material passes therethrough into a discharge passage 22 formed at one side of the drum. At the bottom of said passage or chamber 22 is disposed an auger 23 for discharging the ground material from the machine in a manner well understood in this art.

It so happens under the high speed rotation of the rotor [9 that finely ground material is forced out of the drum adjacent the hinge l4 through the gap between adjacent ends of the screen sections l1 and I2. This is highly objectionable for many reasons and; therefore, a seal 24 is provided in the form of a short length of imperforate sheet metal plate securely fastened by appropriate bolts 25 to the end of the screen section [1 adjacent the hinge M. This plate 24 is located on the outer surface of the screen IT, as shown, and has an extended end overlapping the gap be tween the adjacent ends of the screen portions. Further, the free end of said seal plate is slightly turned up, as at 26, for properly guiding the seal plate on to the adjacent edge of the screen section I2 as the cover 16 is swung from its raised position to its lowered position.

The plate 24 is preferably slightly arcuated, so that it will fit down snugly against and conform to the shape of the screens. It is also desirable to countersink the heads of the bolts 25 on the inner face of the screen I! to leave a smooth surface.

From this disclosure it can now be seen that the seal 24 snugly overlaps and bridges the gapped adjacent ends of the screen sections l1 and I2 when the cover I6 is closed, to prevent 55 blowing out and leakage of material past the hinge l6 when the mill is in operation.

It is the intention to cover all changes and modifications of the example of the invention hereinshown and described for the purposes of disclosure which do not in material respects con stitute departures from the spirit and scope of the invention as covered by the appended claims.

What is claimed is: j

1. Ina mill comprising a drum'with a portion thereof pivoted thereon to provide a hinged cover, and a pluralityf of curved screen sections disposed therein in end to end relation to provide a substantially continuous cylindrical screen Within the drum andcover, .a screen section carried by the cover section abutting a screen section carried by the druirn substantially in alignment with the hinge point of the cover, said two screen sections being thereby separable when the cover is opened, the combination with'one of the screen sections of a seal carried thereby, said seal being formed of imperforate sheet metal and having a portion thereof curved to provide a surface as a section of the aforesaid cylinder, said seal being then 'curved radially outward from the cylinder to provide a guide portion for guiding the seal over the adjacent screen section when the cover is closed on the drum, the screen sections being thereby replaced in normal end to end position, said seal closely over-lying the junction of said two screen sec-tions, I

2. In a mill comprising a drum with a portion thereof pivoted thereon to provide a hinged cover, and plurality of curved screen sections disposed therein in end to end relation to provide a substantially continuous cylindrical screen within the drum and cover, a screen section carried by the cover abutting a screen section carried by the drum, said two screen sections being thereby separable when the cover is opened, the combination with one of the screen sections of a seal carried thereby, said seal being formed of imperforate sheet metal and having a portion thereof curved to provide a surface as a section of the aforesaid cylinder, said seal being then curved radially outward from the cylinder to provide a guide portion for guiding the seal over theadjacent screen section when the cover is closed on the drum, the screen sections being thereby replaced in normal end to end position, said seal closely'over-lying the junction 'of said two screen sections.

35in a mill comprising a drum with a portion thereof pivoted thereon to provide a hinged cover, and 'a plurality of curved screen sections disposed therein in end to end relation to provide a substantially continuous cylindrical screen within the drum and cover, a screen section carried by the cover alt-flitting a screen section carried by the drum substantially in alignment with the hinge paint of the cover, said sections being thereby separable when the cover is opened;'the combination with one of the screen sections nf a seal carried thereby, said seal being formed of imperforate sheet metal and having a portion thereof curved to provide al surface substantially as a section of the aforesaid cylinder, being slightly curved radially inwardly ltherefrom, said seal being then curved radially outward from the cylinder to provide a guide portion for engaging the adjacent screen section and guiding the seal thereover when the cover is closed on'the drum, the screen sections being thereby: replaced in normal endj 'to end position, said seai closely overlying the' ju'nction of said twoscreen sections.

4. In a mill comprising a drum with; a portion thereof pivoted thereon to provide a hinged cover, and a plurality of curved screen sections disposed therein in end to end relationto PI'OVidQgEL substantially continuous cylindrical screen within the drum and cover, a screen section carried by the cover abutting a screen section carriedby the drum, said sections being thereby separable when the cover is opened, the combination with one of the screen sections of a seal carriedlthere by, said seal being formed of imperforate sheet metal and having a portion thereof curved to provide a surface substantially as a section of. the aforesaid cylinder, being slightly curved radially inwardly therefrom, said seal being then curved radially outward from the cylinderv to provide a guide portion for engaging the adjacent screen section and guiding the seal thereover when the cover is closed on the drum, the screen sections being thereby replaced in normal end to end position, said seal closely over-lying the junction of said two screen sections;

RAYMOND D. MACDONALD. 

